Metal-casting.



mt an arms 1 PATENT j OFFICE.

EZECHI'EL WEINTRAUB, 0F LYNN, MASSACHUSETTS, ASSIGNOR TO GENERAL ELEC- TR IC COMPANY, A CORPORATION Q]? NEW YORK.

Patented Apr. 16,- 1912.

METAL-CASTING.

1,023,604. Specification of Letters Patent.

No Drawing.

To all whom, it may concern:

Be it known that I, Eznonmr, VVEINTRAUB, a citizen of the United States, residing at Lynn, in the county of Essex, State of Massachusetts, have invented certain new and useful Improvements in Metal-Casting, of which the following is a specification.

This application is a continuation in part of my prior application, Serial No. 524,949, filed October 27, 1909.

My present invention relates to the purifying and casting of metal and is applicable to copper or its alloys, and to other metals as for ,example silver. v

Forimany years there has been a demand for copper castings free from blow holes, and of good electrical conductivity. Copper, when in molten condition, dissolves oxygen, nitrogen, carbon monoxid, and other gases, and the gases are setfree on cooling, thus reducing blow holes, and greatly impairmg the mechanical strength and decreasing the electrical conductivity of the cast cop er. Silver acts in a similar manner. Furter, molten copper containing dissolved ses does not flow freely in a mold and Will not take sharp outlines. The addition of aluminum, magnesium, phosphorus, and other materials to the melted copper has been tried for removing the gases by chemical combination.- Unfortunately, however, all these substances alloy readily with copper, and slight traces of any of these elements in the copper will greatly lower the electrical conductivity of the same.

Pure boron, or any boron compound in which the state of oxidation of boron is' lower than its usual one in boric' anhydrid, ossess properties which make them peculiarly useful for the solution of the important technical problem of producing sound copper castings of high conductivity. These properties are: first, a high aflinity for oxygen, nitro en and various other gases; secend, no ciemical affinity for copper, and third, the property of forming an easily fusible slag of boric anhydrid.

By the expression state of oxidation lower than the anhydrid, I mean to include boron material which is capable of being oxidized to form boron trioxid,in other words, a

. alternating current are maintain Application filed June so, 1911. ,Scrial no. 636,270.

boron material which is in ,a condition favorable for combination with oxygen, and, other dissolved gases. This -term -would therefore include such material as boron earbid which is capable of being oxidized to form boron trioxid. Of course, as pointed out above, the addition of substances capable of alloying with copper mustbe avoided,

I have found that if I add to the crucible of molten copper of ordinary chemical purity a small quantity of boron varying be tween of one per cent. and 0 one per cent, or a boron compound containlng an equivalent amount of boron in a reduced state, that is, in a' state of oxidation lower than its usual one, B 0 the castings are.

free from blow holes or flaws, and have an electrical conductivit as high as 95 or 98 per cent, of the Matt iessen standard. The castings reproduce faithfully all the details of the mol If pure boron is to be used for treating the copper prior to castin it is obtained by reducing boron chlorid with hydro en in an between the water-cooled cop er electrodes, all of which, is fully descrl ed by mein my copending application, vSerial No. 524,939, filed Oct. 27, 1909. Processes for obtaining elemental boron are also described in my previous Patents Nos. 997,87 9, July 11, 1911, and 1019392, March 5,1912. However, for

the purpjose of my invention the additioii of ure oron is not necessary. The carbid of oron is entircl suitable for carryiig out my invention. oron carbid is prepar by heatin asuitable mixtureof boric oxid, B, O,, an carbon to the reaction temperature in an electric-resistance or are furnace or by any other suitable means, the process being analogous to the well known process of making silicon carbid. Care must be taken to, start with pure raw materials and so to carry out the o eration that no impurities are introduc such as silicon, aluminium, etc., which would lower the conductivity of the cast copper or silver. .By working with reaction mixtures of considerable quantity ayery pure product can be secured by reyacting the outer portions of one per cent. depending u on the contentv of boron in the carbid, on e nature of the mold, the nature of the metal to be cast, etc.

While in the preferred form of 'my invention I use the carbid of boron as described above I may employ with equally good results, the product of the reaction between magnesium and boric anhydrid.

' This roduct is a. material rich in boron and containing magnesium or oxygen, dependm upon the conditions of, the reaction.

en the reaction between the -boric anhydrid and the magnesium is carried out with the use of an excess of boric anhydrid and at a temperature of 1300 C. or preferably higher, the roduct, after being washed with dilute su furic acid to dissolve out magnesium borate and unacted upon boric anhydrid, is substantially free from ma esium. It is a substance of somewhat variable composition but its com osition a roximates that required by te formu a ,0. It, therefore, may be termed a suboxid of boron. This substance because of its low degree of oxidation is a deoxidizer and is converted to the form of boric anhydrid B 0, The same holds true if the boron contains magnesium, as is the case when the above reaction is carried out with no excess of boric anhydrid or when the temperature is relativel low. As only a sma 1 amount of boron is required to bring about the beneficial result in the copper, the amount of magnesium introduced into the copper is negligible and it afiects but little the.conductivity. While boron carbid possesses advantages as a deoxidizing and de- Easifying material over the suboxid of oron on the one hand by its cheapnem and over the hnpurified m nesium reduction product of boric anh dri byv reason of be- *mg cheaper, non-by opic and by yieldless slag, these latter substances may be used to good advantage in the casting of copper.

' As a convenient method of introducing boron into the copper I place the boron ma terial in the bottom of the crucible or mixed with pure charcoal and cover it with the metal to be melted. During the process of melting the deleterious gases are removed from the fusion by the boron material and the fused slag consi ng la 1y of boric acid is retained by the charcoa The boron giatg'iaijl alsgl may be conveniently ilnstflpuc yin osmg' 'itinacopperca e and stirring it into the melt.

The copper is not injured by the addition.

melts containing .is uncertain and cm e, and requires slcilled' pot.

of an excess of boron, as the excess of boron does not combine with the copper but either burns and collects as a sing at the top of the copper or else remains as traces in the copper merely as mechanical admixture and therefore not affecting appreciably its properties.

While my process may be practiced by simply melting the copper in contact with the boron material it is preferable in some instances to superheat the melted copper, especially when stirring the boron material into the copper and when using a sand mold. The melting point of copper is about 1080 C. and it 18 common practice to pour the 30 molten metal at a temperature of about- 1100 C. By the term superheat I mean a temperature considerably above this point. This temperature may be as high as 1350 C. or even higher. The amount of super heat will be governed by the conditions under which the casting is made. The pouring temperature, of course, will be governed by the degree of fluidity desired in the metal and will vary'with the nature of the casting.

By the practice of the described process I have made copper castings which I term boronized castings in complex sha e, such, for instance, as yokes for electrics recording meters. hese are made either in sand molds, or in preheated iron molds, and in the latter case were so complete in detail as to need little or no machining before being put in place in the meter. Induction motor rotors of the squirrel-cage type can readily be made, the rings -and transverse conductors being cast all at a single melt directly in place on the machine core. Copper al oys, such as gun metal and bronze are also bene fited by the additions of small quantities of boron just before pouring. In general, the advantage of the boron treatment extends to uses, such as oxy en, nitro on and the like, either combine or free, but of such composition that the boron will not unite directly with the metal or metals of the melt to forma boride.

While in the ordinary foundry this method represents the'one wa of producing sound cop 'r castings of big conductivity, a process, own as ling is at present utilized'in the operation of smelting the crude copper and cop r ores, This process labor, and frequently leads to over 0 or underpo'ling, and the copper thereby has on an average a conductivity of about 85 per cent, on account of the evolved by the green poles employed in the process. I wish it to be understood that my process of casting copper with the use of oron applies egually well to preparing copper for casting in the smelting operation.

t has a decided advantage over the poling method, it is reliable, giving always the 130 same results; requires no skilled labor, and produces a better cast metal.

What I claim as new and desire to secure by Letters Patent of the United States, is

1. The method of removing gases contained in molten metal with which boron does not readily combine which consists in adding thereto a boron material in an oxidiz able state While said metal is molten.

2. The method of treating metal with which boron does not combine which consists in adding to the metal while molten a non metalliferous boron material in a condition capable of combining with gaseous impurities, the amount of said material being slightly in excess of that required to eliminate the impurities.

3. The method of treating copper which consists in incoporating therein, while molten, a boron material in a condition capable of combining with oxygen and of a quantity sufiicient to free the resulting product from undesired compounds and gases.

4. The method of treating molten copper bearing metal which consists in incorporating therewith boron material in a state of oxidation lower than boric anhydrid.

5. The'method of treating molten copper containing impurities which consists in incorporatin with said copper boron in a state of oxidation lower than boric anhydrid and proportioned to leave in the resulting product not to exceed one-tenth of one per cent. boron.

6. The method of increasing the conductivity and soundness of cast copper which consists in adding to the copper while molten boron material in a state capable of combining with oxygen or other gaseous im purities, said material being proportioned to leave in the resulting product not to exceed traces of boron material uncombined with the copper.

7. The method of treating a fusion containing a metal of the copper group which consists in incorporating therein While heated to a temperature considerably above its melting point, a quantity of an oxidizable boron material sutficlent to free the resultin product from undesired compounds and gases.

8. The method of increasing the conductivity and soundness of cast copper which consists in incorporating with the copper while heated to a temperature of about 11001350 C. a material containing boron in an oxidizable condition.

9. A firm, dense casting of high electrical conductivity consisting of copper freed from dissolved gases and containing boron material in traces, uncombined with copper.

10. A copper casting characterized by a conductivity of at least 95 er cent. and a sound structure free from Blow holes and containing traces of boron material uncom bined with copper.

11. As an article of manufacture, a metallic body consisting largely of copper and containing traces of boron uncombined with said metallic body.

12. The method of treating copper which consists in incorporating therein, while molten, a boron material, non-alloyable with copper, and capable of combining with gaseous impurities.

In witness whereof, I have hereunto set my hand this 27th day of June, 1911.

EZEOHIEL WEINTRAUB.

Witnesses:

JOHN A. MCMANUH, Jr., FRANK G. HATIIE. 

